This invention relates to an improved railcar connector assembly and more particularly to a freight railcar drawbar assembly and an elastic spacer therefore.
Railcar connections are made of steel and must be able to withstand large buff (retarding) and draft (pulling) loads yet be able to angle horizontally and vertically and to twist at the car sill interconnection so as to permit adjacent cars to negotiate turns and inclines and to rock transversely. In some special applications, such as coal carrying railcars, the connectors between sucessive cars must permit rotation of a car about its longitudinal axis for dumping its load. Furthermore, upon buff and draft impacts, the connections should essentially absorb movement due to longitudinal slack (the spacing between parts), such as by a cushioning draft gear, or be substantially slack free. In freight rail car connectors a popular slack free arrangement incorporates a wedge that is gradually inserted between connector and car sill parts to compensate for initial spacing and for wear that occurs during operation. Usually the wedge is located between a follower block and a sill pocket wall. Examples of slack free wedge type connections are described in U.S. Pat. Nos. 3,716,146; 4,258,628; 4,456,133 and 4,549,666.
A problem with some railcar connections is that the connector parts are maintained so tight as to bind and hinder angling and twisting of the connector even when under draft loading especially in a new condition. This is particularly troublesome between adjacent parts that are manufactured with multiple or complex curves on bearing surfaces or where the centers of curvature of the bearing surfaces do not precisely coincide. Drawbar connectors present such problems; and slack free connectors employing wedges are particularly subject to this problem when the connector undergoes maximum draft loading and the wedge efficiently moves between parts. Rotary connectors employing gravity fed wedges also present a problem that the wedge may become withdrawn or cocked when it is temporarily inverted.
Therefore, it would be advantageous to allow limited slack to occur between connector parts generally, and particularly with respect to wedged connectors where limited slack occurs without compensatory movement of the wedge. A prior attempt to accomplish this in a wedged slack free connector is described in U.S. Pat. No. 4,258,628 wherein two vertical elastomer strips are seated in vertical grooves at each side of a wedge contacting face of a follower block in an articulated rail car connection. However, the amount of elastomer that may be utilized in such an arrangement is relatively small resulting in low resistance and chase to wedge movement; and the dual arrangement of resilient strips may cause undesirable angling of the wedge under certain conditions when the connector is angled horizontally under draft load. Moreover, this arrangement, upon failure of either one of the elastomer strips, may require replacement of a follower block that has become beneficially honed to the shape of a connector butt end through usage.
Cushioning draft gear may ameliorate the problems in some connectors, such as couplers where commonly used. However, draft gear is relatively expensive and heavy; and, accordingly, it would be advantageous to provide for limited slack and elimination of the draft gear.